1. Field of Invention
The present invention relates to a method of testing radiation. More particularly, the present invention relates to a method of testing radiation for a SDRAM.
2. Description of the related Art
In the field of space technology, electronic devices that are utilized in space have to be tested with an anti-radiation test. In wireless satellite transmissions, for example, the electronic devices used for satellite communications have to pass a radiation test. Those devices have to have high resistance to radiation and good readability for use in space.
The radiation test for a synchronized dynamic random access memory (SDRAM) is very important, because the SDRAM is an important device for transmitting data. There are various methods that can detect the damage of a SDRAM and its reliability during the radiation process. In general, in a single event upset (SEU) method, when the SDRAM is radiated, the written status of the SDRAM will change. However, when the status of the SDRAM is rewritten, the SDRAM can still function. In a single event latchup (SEL) method, after the SDRAM is radiated, the SDRAM cannot function. However, when the SDRAM is restarted, the SDRAM can function again. Micro latch-up and get rapture tests are more reliable tests used to test the SDRAM and can obtain more details about the tested device. The micro latch-up test detects the location of a non-functional region in the SDRAM after the SDRAM has been radiated and tested, but the SDRAM does not have to restart its program. The get rapture test can indicate whether the SDRAM is permanently damaged after the radiation test.
With the increasing improvement of semiconductor technology and the demand of higher speeds for computers, there has been gradual development in the memory capacity of the SDRAM device. However, a SDRAM is still a newly developed device, so currently there is no literature regarding how a SDRAM will be affected under a radiation test. Therefore, the condition of a SDRAM that is subjected to the radiation test is still unknown.
It is an object of the present invention to provide a method of testing radiation for a synchronized dynamic random access memory (SDRAM). The method comprises performing the SEU, the micro latch-up, the SEL and the get rapture tests on the SDRAM. Thus, the condition of the SDRAM after the radiation test can be determined, and the reliability of the SDRAM can be improved.
It is another object of the present invention to provide a method of testing radiation for a SDRAM. The method comprises performing a self-test by a test device to ensure that all the test devices are functioning properly. A xe2x80x98startxe2x80x99 signal is transmitted from an irradiation controller to an irradiation room, and periodic radiation is produced continuously. Each cycle of the periodic radiation consists of on/off regions. The test device checks whether the SDRAM is in an off region. If no radiation is detected on the SDRAM, a test pattern is then written from the test device to the SDRAM. The readings obtained from the SDRAM are calculated to obtain a difference sum. When the SDRAM is in an on region, wherein radiation is detected on the SDRAM, the test device checks if there is an abnormal current present in the SDRAM. If there is an abnormal current present in the SDRAM, the test device goes back to its self-test step. However, if there is no abnormal current present in the SDRAM, the test device checks whether the SDRAM is in an off region. Once the SDRAM is in the off region, a test pattern is written from the test device to the SDRAM. Readings, which are obtained from the SDRAM before and after the test, are calculated, and a difference sum of these readings is obtained.
The test device checks whether a xe2x80x98stopxe2x80x99 signal is sent out by the radiation controller, if the radiation controller dose not send out the xe2x80x98stopxe2x80x99 signal, the test process goes back to the step of writing a test pattern from the test device to the SDRAM, and the readings, which are obtained from the SDRAM before and after the test are calculated, wherein a difference sum of these readings is obtained.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.